Abstract: :
Purpose:The immune privilege of the eye is characterized bythe lack of APCs. However, they were detected even in the centerof normal murine corneas by a new approach for surface-parallelslicing of the corneal stroma. Topical dexamethasone pretreatmentand ballistic gene transfer were studied for their effect onthe number of corneal APCs and graft survival after keratoplasty.Methods:The epithelium was removed with EDTA, and frozen sectionsof the remaining stroma were sliced parallel to the outer surfaceof the vaulted cornea on a frozen tissue tek log. The central2.5 mm of these sections and the epithelial flatmounts wereexamined immunohistologically for F4/80+ cells and MHC classII+ cells in 3 groups of 6 BALB/c mice each. Graft survivalafter orthotopic keratoplasty (donors: C3H mice, recipients:BALB/c mice) was determined in the same groups: 1. No treatment(controls), 2. Topical dexamethasone pretreatment for 7 days,3. Gene gun treatment 24 hours before transplantation.Results:Theuntreated corneas had 115.7±33.7 F4/80+ and 106.8±46.2MHCII+ cells in the epithelium and 48.9±13.2 F4/80+ and7.3±5.5 MHCII+ cells in the stromal layer. Dexamethasonepretreatment reduced the positive cells in the epithelial flatmounts(1.8±0.6 F4/80+ and 2±1.7 MHCII+ cells) but notin the corneal stroma. Graft survival was 16±4 days inuntreated mice and 16±3 days after dexamethasone pretreatment.Ballistic gene transfer increased the stromal F4/80+ cells (164±91.6,p<0.01). Graft survival after gene gun transfection of donorand recipient corneas with mIL-4 and mCTLA4 (27±19 days)was the same as in the untreated group (27.4±16.8 days)but significantly increased to 64±28 days (p<0.01)when treating only the recipient.Conclusion:The outcome ofcorneal transplantations is determined by APCs. Ballistic genetransfer triples the F4/80+ cells in the corneal stroma. Thefavorable effect of gene statement is counteracted by allogenaugmentation when the donor cornea is treated. Thus ballisticgene transfection of the corneal epithelium with mIL-4 + mCTLA4is only effective when restricted to the recipient. Steroidpretreatment dramatically reduces the epithelial but not thestromal APCs and has no influence on graft survival.